Replication: creating accounts

I have some doubts regarding sql replication. I have followed microsoft tutorials for replication.

They are http://technet.microsoft.com/en-us/library/aa337433(v=sql.105).aspx and some other links http://technet.microsoft.com/en-us/library/aa337473(v=SQL.105) etc..

In the first link it is given as create 4 windows account at publisher and 2 accounts at subscriber.Does this accounts like repl_logreader are needed? Because i hav never seen using this account in any steps in replication tutorial.repl_snapshot and repl_merge are used for running snapshot agent in the tutorial given.Why this repl_merge account is needed?

I hav done merge replication and its working.But Where does logreader agent run in replication process? Its not mentioned in the tutorial!!

Also can i setup replication only by using sql user accounts without using any of windows accounts?

thank u..